The sum of the present age of the father and his daughter is 42 years. 7 years later, the father will be 3 times older than the daughter. The present age of the father is:

Let the present age of father is x.
$\therefore$Present age of daughter $=(42-n)$ years.
According to the question,
$$\begin{gathered} (x+7)=3\times (42-x+7) \\ x+7=147-3x \\ 4x=147-7 \\ x=35 \end{gathered}$$
So, Present age of father is 35 years.